Rotary kiln



F; W. CORKILL Feb. 21, 1933.

ROTARY KILN Filed Aug. 12, 1929 f? TTOBA/EY Federated Feb. 21, I933 srAT FREDERICK W. GOBKILL, OF LOS ANGELES, CALIFORNIA, .A SSIGNOR TOPACIFIC COAST BORAX COMPANY, A. CORPORATION OF NEVADA ROTARY KILN'Application filed August 12, 1929. Serial No. 385,274.

This invention has to do with the art of calcination, and is directed toimprovements in the construction of rotary kilns, whereby lit? theeficiency of such kilns and the uniformity and quality of the calcinedproduct are greatly increased.

The usual construction of rotary kilns consistsof an elongated tubularshell, which is supported upon rollers and is provided with means forintroducing material to be calcined at one end of the shell and withmeans for receiving the calcined material at the opposite end of theshell. Means are provided for rotating the shell at any desired speed,

and it is theusual practice to incline the shell slightly away from theend at whichthe material to be calcined is introduced.

The shell may be heated either externally or internally. It is the usualpractice in the use of rotary kilns, however, to supply the heat bymeans of a burner placed atthe outlet end of the shell and adapted todirect a flame through the shell which is counter current to thedirection of movement of the material therein.

In the use of kilns of this nature, the material to be calcined is firstcrushed to a size at which it may be conveniently handled, and thecrushed material is introduced into the shell through suitable means,the inclination of the shell and the speed of rotation being such as toproduce the desired extent of calcination of the particular materialwhich is being used. 7

One 'ofthe most serious difiiculties which has been encountered in theuseof kilns of this nature resides in the fact that it is economicallyimpossible to produce a crushed ifthe kiln is operated so as to'properlycalcine the fine material, the coarse material must be separatedtherefrom after the calcining step and must be subsequently subjecttoeither screen the crushed material before it is introduced into the kilnso that the material has a substantially uniform fineness, or toscreenthe calcined material after it comes from the kiln and subject thecoarse material t9 a second calcination step. Such an operation inconnection with ores in which the calcination must be more or lessaccurately controlled to obtain the proper results, is obviouslyimpracticable, and in any event is ineflicient and expensive.

It is a primary object of this invention to produce a rotary kiln inwhich the movement of the coarse material through the kiln is retarded,the retarding means being in the formof an obstruction or a plurality ofob structions, which are adapted to permit a substantially uninterruptedpassage of fine material through the kiln, but which at the same timeretard the movement of the coarse material so that both the fine and thecoarse material receive the proper calcination.

It is also an object of this invention to produce a rotary kiln which isprovided with baflies, associated with theobstructions mentioned abovein a manner such that the flame passing through the'kiln is directedinto engagement with the material passing over the obstruction, greatlyincreasing the thermal efliciency of the unit.

Details in the construction of my invention, together with other objectsattending its productionfwill be better understood from the followingdescription of the accompanying drawing, in which Fig. 1 is a sectionalelevation, showing a preferred embodiment of my invention.

Fig. 2 is an end elevation, which may be considered as having been takensubstantially in the direction of the arrow 2 in Fig. 1 v

Fig. 3' is a sectional elevation which may be considered as havingbeentaken in a plane represented by the line 33 in Fig. 1,

tially in a plane represented by the line -5 in Fig. 1, and illustratesthe manner of 'ar- Q. ranging the-baflles in the shell.

More particularly describing the invention as herein illustrated,reference numeral 11 indicates an elongated shell, ,which is supportedby means of rollers 12 and 12, enga 15 ing annular; channels 13 and 13,mounted upon the outer surface of the shell.

The shell 11 is adapted to receive rotation through the medium of agear-14, mounted upon its outer surface and engaginga pinion 15,which-is adapted to be driven through the medium of 7 drive shaft 16from any suit able sour of power (not shown).

It will be noted in Fig. 1, as was heretofore pointed out, that theshell 11 is set at a slight inclination, so thatthe material entering atthe end 17 through the hopper 18'will pass downwardly through the shellduring its ro-. tation, and will be delivered from the outlet 7 end 19into a receiving hopper 20, from which it may be delivered onto aconveyor belt, such as is indicated byreference numeral 21.

Means for heating the material within the shell are illustrated as beingin the formof a burner 22-, which is positioned at the outlet end of theshell, and may be supported in' any well knownmanner.

The inlet end of the shell is shown as being' surrounded by a draftchamber 23,'which is provided with-an outlet pipe 24, which, in 4 turn,may have a natural draft, or may be providedwith a fan 25 for providinga forced raft through the shell.

It will be understood by'those familiar with the art that theconstruction so far described is common to rotary kilns such as are nowin use, and that the essence of my invention resides largely in meansfor governingthe passage of the material through the kiln. Such means,as has heretofore been. pointed out, comprises an obstruction or alurality of obstructions so constructed an so positioned within the kilnas to permita substantially uninterrupted passage of the fine materialthrough the shell, and at the same time to retard the passage of thecoarse material therethrough. Such obstructions are,in the formillustrated, shown as comprising annular screen members 30, which arepositioned in spaced relation with each other throughout the length ofthe. shell, and are retained withthe shell in any suitable manner, suchas'by means of angular straps 31.

It was also mentionedas an object of this in vention to provide theshell with baflle means,

c3 whereby the bet gases passing through the shell would be directedinto engagement with the material assing over the screens orobstructions. uch baflles are indicated in the drawing by referencenumeral 32, and are shown as being in the form of circular plates,supported b angle straps 33, and positioned so that the ame passingthrough the shell is projected against the baflle and must pass over thematerial which is held back by the screens or obstructions 31.

In the use of my invention, it will be apparent that the material to becalcined, which -is introduced into the shell through the hopper 18will, during the rotation of the shell, pass downwardly toward theoutletend 19. a

The screens 31 permit the passage of the fine material, and it will beunderstood that the mesh of the screens and the number and arrangementthereof will be governed entirely by the quality and properties of themate-, rial which is belng calcined in the kiln. The

' coarse material will, of course, build up be hind the screens and itspassage through the shell will, accordingly, be retarded, so that itwill be completely calcined before it is delivered from the outlet end19.]

It is to be understood that, while I have herein described andillustrated one preferred embodiment of my invention, the same is-notlimited to the precise construction set forth,

' but includes within its scope whatever changes fairly come within thespirit of the appended claims. v

I claim as m invention 2' 1. A'rota'ry comprising: anelongated tubularshell; mearis'for rotating said shell; means for injecting a flame intoone of said shell; means. for introducing material to be calcined intotheother end of said" shell a plurality of annular screens mountedinsaid shell, adapted-to permit a substantially unin- V terruptedmovement of fine material through said shell and at the same time retardthe movement of the coarse material 'therethrough; and baflles mountedinthecenter of said shell adjacent said annular screens for directingthe hot gases passing. through said" shell into contact with thematerial passing over said obstructions. r

2. Arotary kiln 'comprising:.an elongated tubular shell; means forrotating. said shell; means'for injecting a flame into one end of saidshell; means for introduc' material to be calcined into the'other end ofsaid shell; a

ioo

plurality of annular screens mounted in'said shell adapted to permit apassage of fine material therethrough and amovement of coarse materialthereover; and a baflle associated w th said screens to deflect heatupon said coarse material. 1

In testimony whereof; I have hereunto set my hand at Los Angeles,California, this 30th day of'July, 1929.

FREDERICK w. poRKtLL. 1:0

